I've tried many test kits - I thought FasTest and SeaTest by Aquarium Systems were pretty good for pH, amm, trites & trates, but their alk, phos and calcium were hard for me read the color changes.
A couple weeks ago I bought all new Salifert test kits and they are IMO ...BY FAR the easist to use.
No guessing
No wondering when the color turned from dark pink, to a faded pink, to a sorta pinkish blue then finally to blue .... it changes color completely with the last drop.
Much easier and faster testing water now
Got several Rio's
, but they all ended up in the closet with all the other misfit toys <img src="graemlins//yeahright.gif" border="0" alt="[yeahright]" />
Mag Drive's are good as mentioned.